This invention relates to a door-closer, and more particularly to a simple pneumatic door-closer.
A door-closer is a familiar device which can automatically close an opened door. The simplest type of door-closer works merely with a coil spring which has a short useful lifetime. This type of door-closer has the disadvantage that the door is shut rather violently. Pneumatic and hydraulic door-closers have been developed to overcome this problem in accordance with the principle of a shock absorber. Although the door can be closed slowly by such door-closers, the manufacturing cost of the door-closer is increased.